CN118130367A - Novel three-pipe tower damage identification method based on strain statistical moment - Google Patents
Novel three-pipe tower damage identification method based on strain statistical moment Download PDFInfo
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Abstract
The invention relates to the technical field of damage identification, in particular to a novel three-pipe tower damage identification method based on strain statistical moment.
Description
Technical Field
The invention relates to the technical field of damage identification, in particular to a novel three-pipe tower damage identification method based on strain statistical moment.
Background
The novel three-tube communication tower comprises a tower bottom base tower column, a cross rod, an inclined rod, an antenna bracket, a lightning rod and a tower column sleeving device, and is widely applied to the field of signal communication and is mainly used for erecting an antenna.
In the process from construction to service of the three-pipe tower structure, rigidity is continuously damaged under the actions of wind load, earthquake load, artificial impact load, fatigue load and chemical corrosion, so-called structural damage is generated, when the damage is accumulated to a certain extent, the stress performance of the whole structure is negatively affected, serious personnel casualties and property damage are caused even by serious personnel to finally lose effectiveness of the structure, in order to ensure safe operation of the structure, an effective method for detecting early damage of the structure is established, an early warning mechanism is established, so that the structural damage is discovered and repaired in early stage, and serious accidents are avoided.
The structural parameters caused by structural damage often cause the structural modal parameters (including modal frequency, modal shape and modal damping) to change, so that the vibration-based damage identification method often adopts the modal parameters and other parameters derived from the modal parameters as structural damage indexes, however, the mode-index-based damage identification method has the biggest defects that the damage identification method is insensitive to local damage and very sensitive to measurement noise.
Disclosure of Invention
The invention aims to provide a novel three-pipe tower damage identification method based on strain statistical moment, and aims to solve the technical problems that the existing damage identification method based on modal indexes is insensitive to local damage and very sensitive to measurement noise.
In order to achieve the above purpose, the invention provides a novel three-pipe tower damage identification method based on strain statistical moment, which comprises the following steps:
step one: a plurality of sensors are uniformly distributed on a three-pipe tower to serve as measuring points, and the sensors are used for collecting strain fourth-order statistical moment values of the measuring points under wind speed and wind direction at a certain moment;
Step two: calculating the strain fourth-order statistical moment value of each measuring point under the wind speed and the wind direction at a certain moment, and setting the moment as an initial value;
step three: under the condition that the wind speed and the wind direction are unchanged, acquiring the strain fourth-order statistical moment value again, and calculating with an initial value to obtain a strain fourth-order statistical moment change rate D as a reference value;
Step four: and calculating the strain fourth-order statistical moment change rate D of the three-tube tower structure under the damage working condition, drawing a D value bar chart, and judging the damage area range of the three-tube tower through the maximum measuring point of the D value.
Wherein the measuring points in the first step are arranged on beam units with complex stress combinations, namely the positions of cross bars on the three-tube tower.
Wherein the measuring points in the first step are arranged at all the cross bar positions on the same plane of the three-pipe tower.
The strain fourth-order statistical moment value in the first step is extracted according to a first-order modal parameter which is easier to obtain by the structure of the three-tube tower, and the D value is calculated and analyzed based on a signal after the structure first-order frequency filtering.
The calculation formula of the strain fourth-order statistical moment change rate D in the third step is as follows:
Wherein: Is the strain fourth-order statistical moment value when i measuring points are lossless,/> Is the strain fourth-order statistical moment value when the i measuring point is damaged.
The judging method of the damage area range of the three-tube tower comprises the following steps: when the wind speed and the wind direction are unchanged, namely external excitation is unchanged, judging damage of the three-pipe tower according to the D value; and when the wind speed and the wind direction change, judging the damage of the three-pipe tower by the change amount of the D value before and after the damage.
When the wind speed and the wind direction of the three-pipe tower change, in order to eliminate the global influence of the wind speed and the wind direction on the change of the D value of each measuring point, the D value reference value caused by the change of the wind speed and the wind direction when the structure of the three-pipe tower is not damaged needs to be compared, and the damage identification of the three-pipe tower is further carried out through the change of the D value.
The invention provides a novel three-pipe tower damage identification method based on strain statistical moment, which provides a strain fourth-order statistical moment change rate damage index, can identify the damage of a local area of a three-pipe tower structure, reduces manual investigation workload, is suitable for quick primary screening of the damage of the three-pipe tower structure, derives the relation between the fourth-order strain statistical moment and the strain energy density based on the strain energy density theory, optimizes the layout of three-pipe tower sensors, reduces labor cost and improves economic benefit.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a new method for identifying damage to a three-tube tower based on a strain statistical moment in accordance with a first embodiment of the present invention.
Fig. 2 is a diagram of a three-tube tower numerical model (8-station) of a new method for identifying three-tube tower damage based on strain statistical moment according to a first embodiment of the present invention.
Fig. 3 is a graph of D values of the strain statistical moment-based three-tube tower damage identification method according to the first embodiment of the present invention under different working conditions at each measuring point.
Fig. 4 is a diagram of a three-tube tower site arrangement and site range for a new method of three-tube tower damage identification based on strain statistical moment in accordance with a first embodiment of the present invention.
Fig. 5 is a flowchart of three-tube tower damage identification for a new method of three-tube tower damage identification based on strain statistical moment according to a first embodiment of the present invention.
Fig. 6 is a graph showing the change of D values of wind speed and wind direction without changing the new method for identifying damage to a three-tube tower based on a strain statistical moment according to the first embodiment of the present invention.
Fig. 7 is a graph comparing D values of wind speed and direction changes under the condition of working condition 1 of the novel method for identifying three-tube tower damage based on strain statistical moment according to the first embodiment of the invention.
Fig. 8 is a D-value change amount graph of wind speed and direction change of the new method of three-tube tower damage identification based on the strain statistical moment according to the first embodiment of the present invention.
Fig. 9 is a different plan view of a three-tube tower of the new method for identifying damage to a three-tube tower based on a strain statistical moment according to the first embodiment of the present invention.
Fig. 10 is a graph showing comparison analysis of identification results of different detection methods of a new method for identifying damage to a three-tube tower based on a strain statistical moment according to a first embodiment of the present invention.
FIG. 11 is a plot of strain time course response at station 1 for the novel method of three-tube tower damage identification based on strain statistical moment in accordance with the first embodiment of the present invention.
Fig. 12 is a graph of the identification result of the new method for identifying damage to a three-pipe tower based on a strain statistical moment according to the first embodiment of the present invention.
Fig. 13 is a graph of the identification result of the new method for identifying damage to a three-pipe tower based on a strain statistical moment according to the first embodiment of the present invention.
Fig. 14 is a graph showing the modal curve difference recognition result of the novel method for recognizing damage to a three-tube tower based on a strain statistical moment according to the first embodiment of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
In the description of the present invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the present invention and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, in the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
First embodiment
Referring to fig. 1 to 14, fig. 1 is a flowchart of a new method for identifying a three-tube tower damage based on a strain statistical moment according to a first embodiment of the present invention, fig. 2 is a diagram of a three-tube tower numerical model (8 measurement points) of the new method for identifying a three-tube tower damage based on a strain statistical moment according to a first embodiment of the present invention, fig. 3 is a diagram of D values of the different measurement points of the new method for identifying a three-tube tower damage based on a strain statistical moment according to a first embodiment of the present invention, fig. 4 is a diagram of a three-tube tower measurement point arrangement and a measurement point range of the new method for identifying a three-tube tower damage based on a strain statistical moment according to a first embodiment of the present invention, fig. 5 is a flowchart of a three-tube tower damage identification method based on a strain statistical moment according to a first embodiment of the present invention, fig. 6 is a diagram of D value change condition that wind speed and wind direction of the new method for identifying a three-tube tower damage based on a strain statistical moment according to a first embodiment of the present invention is unchanged, FIG. 7 is a graph showing the D value of the change of the wind speed and the wind direction under the condition 1 of the strain statistics moment based three-tube tower damage identification new method according to the first embodiment of the present invention, FIG. 8 is a graph showing the D value change amount of the change of the wind speed and the wind direction of the strain statistics moment based three-tube tower damage identification new method according to the first embodiment of the present invention, FIG. 9 is a graph showing the different plane views of the three-tube tower according to the strain statistics moment based three-tube tower damage identification new method according to the first embodiment of the present invention, FIG. 10 is a graph showing the difference detection result comparison analysis of the strain statistics moment based three-tube tower damage identification new method according to the first embodiment of the present invention, FIG. 11 is a graph showing the strain time course response of the strain statistics moment based three-tube tower damage identification new method according to the first embodiment of the present invention, fig. 12 is a graph showing the result of the identification of the new method for identifying a damage to a three-tube tower based on a strain statistical moment according to the first embodiment of the present invention, fig. 13 is a graph showing the result of the identification of the new method for identifying a damage to a three-tube tower based on a strain statistical moment according to the first embodiment of the present invention, and fig. 14 is a graph showing the result of the identification of a difference in modal curve for the new method for identifying a damage to a three-tube tower based on a strain statistical moment according to the first embodiment of the present invention.
The invention provides a novel three-pipe tower damage identification method based on strain statistical moment, which comprises the following steps: the method comprises the following steps:
S101, step one: a plurality of sensors are uniformly distributed on a three-pipe tower to serve as measuring points, and the sensors are used for collecting strain fourth-order statistical moment values of the measuring points under wind speed and wind direction at a certain moment;
s102, step two: calculating the strain fourth-order statistical moment value of each measuring point under the wind speed and the wind direction at a certain moment, and setting the moment as an initial value;
S103, step three: under the condition that the wind speed and the wind direction are unchanged, acquiring the strain fourth-order statistical moment value again, and calculating with an initial value to obtain a strain fourth-order statistical moment change rate D as a reference value;
s104, step four: and calculating the strain fourth-order statistical moment change rate D of the three-tube tower structure under the damage working condition, drawing a D value bar chart, and judging the damage area range of the three-tube tower through the maximum measuring point of the D value.
In the embodiment, the strain fourth-order statistical moment change rate damage index is provided, the damage of a local area of the three-pipe tower structure can be identified, the manual investigation workload is reduced, the method is suitable for the rapid primary screening of the damage of the three-pipe tower structure, meanwhile, the relation between the fourth-order strain statistical moment and the strain energy density is deduced based on the strain energy density theory, the layout of the three-pipe tower sensor is optimized, the labor cost is reduced, the economic benefit is improved, in addition, the method has good noise resistance, the influence on the change of the wind speed and the wind direction is small, and the engineering applicability is verified through the field test, so that the technical problems that the existing damage identification method based on the modal index is insensitive to the local damage and very sensitive to the measurement noise are solved.
Wherein the measuring points in the first step are arranged on beam units with complex stress combinations, namely the positions of the cross bars on the three-pipe tower, and the measuring points in the first step are arranged at all the positions of the cross bars on the same plane of the three-pipe tower.
And secondly, extracting the strain fourth-order statistical moment value in the first step according to a first-order modal parameter which is easier to obtain by the structure of the three-tube tower, and carrying out calculation analysis on the D value based on a signal after structure first-order frequency filtering.
Again, referring to ASCE benchmark steel frame model experimental protocol [22], damage conditions were simulated by removing rods, wherein each of the other intersecting rods except for the 1 st and 2 nd sections was one section, and the three-tube tower can be divided into 18 total sections.
Thirdly, in order to determine the strain statistical moment damage identification area range and the proper number of the sensors, and consider the influence of the distance between the damage part and the measuring point, the following working conditions are set:
working condition 1: dismantling the 1-section diagonal rod (close to the measuring point) of the 5 th section of the structure;
working condition 2: dismantling the 8 th section 1 inclined rod (far from the measuring point) of the structure;
Working condition 3: dismantling the 1-section diagonal rod (close to the measuring point) of the 15 th section of the structure;
working condition 4: and (3) dismantling 1 diagonal rod (far from the measuring point) of the 6 th section and the 13 th section of the structure.
Meanwhile, the calculation formula of the strain fourth-order statistical moment change rate D in the third step is as follows:
Wherein: Is the strain fourth-order statistical moment value when i measuring points are lossless,/> Is the strain fourth-order statistical moment value when the i measuring point is damaged.
In addition, the judging method of the damage area range of the three-tube tower comprises the following steps: when the wind speed and the wind direction are unchanged, namely external excitation is unchanged, judging damage of the three-pipe tower according to the D value; and when the wind speed and the wind direction change, judging the damage of the three-pipe tower by the change amount of the D value before and after the damage.
Finally, when the wind speed and the wind direction of the three-pipe tower change, in order to eliminate the global influence of the wind speed and the wind direction on the change of the D value of each measuring point, the D value reference value caused by the change of the wind speed and the wind direction when the structure of the three-pipe tower is not damaged needs to be compared, and the damage identification of the three-pipe tower is further carried out through the change of the D value.
When the novel method for identifying the damage of the three-tube tower based on the strain statistical moment is used, when the damage identification is carried out on the three-tube tower, a plurality of sensors are uniformly distributed on the three-tube tower as measuring points, the sensors collect strain fourth-order statistical moment values of all measuring points under the condition of wind speed and wind direction at a certain moment, after the strain fourth-order statistical moment values of all measuring points under the condition of wind speed and wind direction at a certain moment are collected, the strain fourth-order statistical moment values are calculated and set as initial values, under the condition that the wind speed and the wind direction are unchanged, the strain fourth-order statistical moment values are obtained again and are calculated with the initial values to obtain a strain fourth-order statistical moment change rate D as a reference value, then a D value bar graph is drawn, and the damage area range of the three-tube tower is judged through the maximum measuring point of the D value.
1. Theoretical analysis:
based on the statistical moment theory, the relation between the structural rigidity and the strain response statistical moment of the three-tube tower structure is deduced. For space truss structures such as three-tube towers, wind load typically plays a major role in control. Under the excitation of the pulsating wind load vector F (t), the motion equation of the discrete multi-degree-of-freedom system can be expressed as follows:
wherein: m, C, K represent the structural mass, damping, stiffness matrices, respectively; x (t) is the time-course response of the acceleration, velocity and displacement of the structure, respectively. The strain and displacement are assumed to have the following linear transformation relationship [19]:
x(t)＝Sε(t) (2)
Wherein: ε (t) is the strain response of the structure, S is the conversion matrix of the structure displacement to strain, and substituting equation (2) into equation (1) and multiplying S T to obtain:
wherein: m ε、Cε、Kε is mass, damping and stiffness matrix corresponding to strain response, and F ε is strain load vector. Let ε (t) =Φ εYε(t),Φε be the strain mode shape matrix, Y ε (t) be the generalized coordinate vector, substituting (3) and multiplying Φ ε T left, we can obtain:
Wherein: wherein/> Is a diagonal matrix,/>Equation (4) can be decoupled for rayleigh damping, i.e., diagonal matrix.
Strain response variance of structure:
If the system is linearly stationary and in an initial rest state, excited by a stationary power spectrum stochastic process with mean value zero, then the mean value of the steady state response of the system is also typically zero, i.e. E [ epsilon i(t)]2 =0, and by the conversion relationship of epsilon (t) =Φ εYε (t), equation (5) becomes:
in the formula (6), the amino acid sequence of the compound, Representing the strain variance of the i-th degree of freedom,/>Nth element representing an ith order strain mode,/>The strain mode coordinate value is represented. Based on the square and open square root mode shape combining method, equation (6) becomes:
Wherein: The response variance of the nth single degree of freedom system equation random reaction is represented.
The decoupled equation of the formula (4) is a single degree of freedom motion equation. The total strain response produced by the single degree of freedom architecture under the strain load f ε (t) is expressed by Duhamel integral:
In formula (8), h ε (t-. Tau.) is a unit pulse strain response function. The autocorrelation function R ε (τ) of ε (t) is expressed as:
Rε(τ)＝E[ε(t)ε(t+τ)] (9)
substituting the formula (8) into the formula (9) to obtain:
Wherein, Is an autocorrelation function of the external load. According to the wiener-Xin Qin formula, the self-power spectral density function of the stable reaction process epsilon (t) is as follows:
Wherein R ε (τ) is the autocorrelation function of ε (t).
The frequency response function has the following relation with the unit impulse response function:
substituting the formula (10) into the formula (11) and combining the formula (12) to obtain:
Obviously have Is a conjugate function of H ε (iω), so the self-power spectral density function of the strain response can be expressed as:
The structural strain response can be found using a self-power spectral density function, namely:
Equation (15) is the variance of the random reaction process response of the single degree of freedom system, based on the above analysis, the multiple degree of freedom system can be decoupled into N single degree of freedom systems, so The strain response variance calculated by the nth equation is represented by the following specific expression:
Wherein H ε,n (iω) is the strain frequency response function of the nth single degree of freedom random reaction equation, the strain frequency response function expression for the nth equation inducing the i-point response at the j-point excitation is as follows [20]:
Wherein: The constants noted as A n,mn、kn and c n are the mass, stiffness and damping, respectively, of the nth single degree of freedom stochastic reaction equation. Substitution of formula (17) into formula (16) yields:
In order to meet the engineering precision requirement, considering that the pulsating wind load is a zero-mean stable random process [21], the power spectrum density function of which is a constant S 0, the formula (16) becomes:
substituting formula (19) into formula (7) for replacement The strain response variance of the ith degree of freedom of the multi-degree-of-freedom system is obtained as follows:
When the structural response follows a gaussian distribution with a mean value of zero, a proportional relationship exists between the even-order statistical moment and the variance. The different-order statistical moment indexes have larger influence on the efficiency and the precision of identifying the damage, the higher the order is, the more sensitive the statistical moment indexes are to the damage, but the stability is reduced, the sensitivity and the stability are comprehensively considered, and finally, the fourth-order statistical moment is selected, namely:
defining a strain fourth-order statistical moment change rate D as follows:
Wherein: Is the strain fourth-order statistical moment value when i measuring points are lossless,/> Is the strain fourth-order statistical moment value when the i measuring point is damaged.
From equations (20) - (22), it can be seen that if the structural rigidity is reduced, the structural modal parameter is changed, so that the strain fourth-order statistical moment change rate D value of the structure is affected. When the wind speed and the wind direction are unchanged, namely external excitation is unchanged, the damage can be judged according to the value D; when the wind speed and the wind direction change, the damage is judged according to the change amount of the D value before and after the damage.
Based on the formulas (7) to (20), the higher-order mode has smaller contribution to the strain statistics moment, the strain statistics moment value can be extracted by depending on the first-order mode parameters which are easier to obtain by the structure, and D value calculation analysis can be further performed on the signals after the first-order frequency filtering of the structure.
2. Numerical simulation
2.1, Three tube Tower model introduction
And establishing a three-tube tower dynamic numerical model by utilizing ANSYS according to a communication tower standard chart set and three-tube tower parameter measurement data provided by China tower stock, inc. The height of the model is 30m, the base width is 2.74m, the tower body is divided into 6 sections, and each section consists of three steel pipes and a plurality of inclined rods. The three-pipe tower material is steel, the elastic modulus E=2.06× 5 MPa, the density rho=7850 kg/m 3, the influence of iron tower bolts, platforms, ladders and the like is considered, the proportional relation between the tower foot support counter force and the total weight of the tower obtained by static calculation under the gravity field of a single tower model is calculated, and the density of the tower body material is multiplied by 1.1[23]. The external excitation adopts a harmonic superposition method to simulate wind load, the design wind speed of the region is 30m/s, the ground roughness is taken as class B, and the wind load is calculated according to a conventional method and then applied to corresponding nodes.
The model adopts a beam-rod hybrid three-dimensional model, the main rod and the cross rod are simulated by beam units, and the inclined rod and other rod members are simulated by rod units. The rod units are only subjected to axial tension and compression, and the measuring points are arranged on the beam units with complex stress combinations, namely the cross rod positions on the three-tube tower. And (3) preliminarily selecting all cross bars on the same plane of the three-tube tower to arrange measuring points, wherein the front third-order frequency of the three-tube tower model and the front third-order frequency error obtained by on-site monitoring data are respectively 0.2%,0.5% and 0.7%, which means that the modeling is reasonable and can be used for subsequent analysis.
2.2, Checking the numerical value
2.2.1 Optimized sensor layout
Referring to an ASCE benchmark steel frame model experimental scheme, damage working conditions are simulated by removing rods, actual conditions such as bolt loosening and the like are further considered, except for the 1 st section and the 2 nd section, each crossed rod is one section, and the three-pipe tower can be divided into 18 sections in total. In order to determine the strain statistical moment damage identification area range and the proper number of sensors and consider the influence of the distance between a damage part and a measuring point, the following working conditions are set:
working condition 1: dismantling the 1-section diagonal rod (close to the measuring point) of the 5 th section of the structure;
working condition 2: dismantling the 8 th section 1 inclined rod (far from the measuring point) of the structure;
Working condition 3: dismantling the 1-section diagonal rod (close to the measuring point) of the 15 th section of the structure;
working condition 4: and (3) dismantling 1 diagonal rod (far from the measuring point) of the 6 th section and the 13 th section of the structure.
The relation between the strain fourth-order statistical moment change rate and the structural rigidity is deduced by combining formulas (20) - (22), and the fourth-order strain statistical moment of the ith degree of freedom under the first-order mode is obtained by taking the first-order mode parameters:
For small strain and linear materials, the strain energy density can be expressed as:
Wherein: u ε is the strain energy density, E is the modulus of elasticity of the material, ε is the strain. According to the mode shape superposition formula epsilon=Φ εYε, the strain value of the ith degree of freedom in the first-order mode is brought into the formula (24) to obtain:
Substituting equation (25) into equation (23) yields the relationship of strain fourth-order statistical moment and strain energy density:
From equation (26), it can be found that the strain fourth-order statistical moment value change is accompanied by a change in strain energy, so that the strain fourth-order statistical moment change rate is directly related to the strain energy, and is in positive correlation, and the larger the strain fourth-order statistical moment change rate of the measuring point is, the larger the strain energy density change of the corresponding measuring point is.
According to the theory, the numerical analysis strain fourth-order statistical moment change rate D of the working conditions 1-4 is shown in the figure 3, and it can be found from the figure 3 that the strain fourth-order statistical moment change rate of the measuring point 3 is the largest when the 5 th section of the working condition 1 is damaged, namely the strain energy density change of the position of the measuring point 3 is the largest when the 5 th section is damaged; the strain energy density of the working condition 2, the 8 th section is damaged, the strain energy density of the measuring point 4 is changed maximally, the 15 th section is damaged, the strain energy density of the measuring point 6 is changed maximally, and the corresponding measuring point value is larger when two parts of the working condition 4 are damaged. The strain energy density change of a certain measuring point is maximized due to different segment damage, the measuring point with the largest strain energy density change is taken as an optimal measuring point, two damage conditions of reducing rigidity of a main rod of the segment and dismantling a diagonal support of the segment are considered, finally, the sensor layout of fig. 1 is optimized to 5 based on energy distribution feedback of measuring point areas, the monitoring range of the optimal measuring point is given, each area with different colors is fed back with the strain energy density of the corresponding measuring point position, namely, 5 measuring areas can cover the whole three-pipe tower, and D value change of each measuring point position can identify whether the local area with the linear color is damaged or not.
2.2.2, Three-tube tower damage identification numerical calculation example
In order to verify the applicability of the method presented herein and to take into account noise disturbances and wind direction variations that may occur in practical engineering, a signal of first order frequency is taken for analysis based on the aforementioned theory. Firstly, strain fourth-order statistical moment values of all measuring points under wind speed and wind direction at a certain moment are calculated, and are set as initial values. Under the condition that the wind speed and the wind direction are unchanged, the strain fourth-order statistical moment value is obtained again, and is calculated with the initial value, so that the strain fourth-order statistical moment change rate D is obtained as a reference value (the value is 0). And finally, calculating the strain fourth-order statistical moment change rate D of the structure under the damage working condition, drawing a D value histogram, and judging the damage area range of the three-tube tower through the maximum D value measuring point. When the wind speed and the wind direction change, the influence on the extracted index is global, the D value of each measuring point is changed, and the local change caused by damage is difficult to judge through the change of the D value of each measuring point. In order to eliminate the global influence of wind speed and direction on indexes, the damage identification can be further carried out through the D value change amount by comparing the damage identification with the D value reference value caused by the wind speed and direction change when the structure is not damaged. And finally, identifying the damage area range of the three-pipe tower by comparing the reference value with the D value under the damage working condition.
According to the operation steps, the set working conditions are shown in table 1, and the wind speeds and directions are simulated respectively under the influence of noise.
Table 1 numerical simulation operating condition detail Table 1List ofnumerical simulation cases
(1) The wind speed and the wind direction are unchanged
And (3) assuming that the wind speed and the wind direction are unchanged, extracting time-course response of corresponding measuring points of the three-tube tower, randomly considering noise working conditions in the table 1, solving a strain fourth-order statistical moment value, and then calculating the D value of each measuring point.
In the case where the wind speed and the wind direction are unchanged, the reference value D is zero. As can be seen from FIG. 6, the maximum D value of the measuring point 2 in the working condition 1 is 1.19, and the damage of the area range of the measuring point 2 can be judged to be consistent with the damage of the working condition 1. In addition, under the noise of 30dB and 20dB, the D value of each measuring point is changed, but the D value of the measuring point 2 is 0.99, and the damage can still be judged to appear in the area range of the measuring point 2; in the working condition 2, the D value of the No. 3 measuring point is maximum and is 0.45, the damage is judged to occur in the area range of the measuring point 3, the damage is consistent with the damage of the working condition 2, in addition, the measuring point 2 also has 0.13 change, because the 8 th section is close to the measuring point 2 at the edge of the area range of the measuring point 3, a certain influence is caused on the measuring point 2, the D value change of the measuring point 3 is maximum, and the damage area range can be further judged to be reduced by further combining the changes of the measuring point 2 and the measuring point 3. After noise is added, the maximum measuring point of the D value has small change, and the whole can still judge that the damage is generated in the area range of the measuring point 3; the D value of the measuring point 4 in the working condition 3 is 1.59, the damage is judged to be in the area range of the measuring point 4, and the damage is consistent with the damage of the working condition 3, and also the 15 th section is close to the measuring point 5, so that the measuring point 5 also has 0.48 change, after noise is added, the area range of the damage in the measuring point 4 can be judged from a result diagram, and the range can be further reduced by combining the data result of the measuring point 5; the working condition 4 can find that the D values of the measuring points 2 and 4 are 0.27 and 0.21 respectively, the damage position is judged to be in the area range of the measuring points 2 and 4, the damage is consistent with the working condition 4, the D value of the measuring point 4 becomes 0.17 after 20dB of noise is added, the noise has a certain influence on damage identification, and the damage range can still be judged as a whole. As can be seen from fig. 6, under the condition that the external excitation is unchanged, the strain fourth-order statistical moment change rate index D value can identify single and multiple injuries of the three-tube tower, can be specific to a regional range, and has a certain noise resistance.
(2) Wind speed and direction change
Considering the change of wind speed and wind direction in an actual engineering structure, the influence of the change of wind speed and wind direction on the damage identification result is simulated. And respectively calculating strain fourth-order statistical moment values before and after the wind speed and the wind direction change under the lossless condition, and constructing a reference value according to a formula (22). And then calculating a strain fourth-order statistical moment after damage, constructing a D value of structural damage according to a formula (22) with the strain fourth-order statistical moment under the lossless condition, and drawing a comparison graph of the reference value and the D value after structural damage under the working condition 1.
Fig. 7 is a comparison chart of the recognition results of the working condition 1, and is a graph of the change between the D value and the reference value of each measured point after damage as the ordinate, so that the structural damage area is difficult to directly judge, and the result is shown in fig. 8.
As can be seen from FIG. 8, the change amount of the D value of the measuring point 2 in the working condition 1 is 0.22, which is obviously larger than the change amount of the D values of other measuring points, and the damage is judged to appear in the area of the measuring point 2, and the recognition effect is less affected by noise; the D value change amount of the measuring point 3 in the working condition 2 is 0.21, so that the damage can be judged to occur in the area range of the measuring point 3, and the influence of noise is small; the change amount of the D value of the measuring point 4 in the working condition 3 is 0.36, and after 20dB noise is applied, the change amount of the D value is affected, but the D value change of the point is obviously the largest in all the measuring points, so that the damage can be successfully identified to appear in the area range of the measuring point 4; and finally, the D value change quantity of the measuring point 2 and the measuring point 4 in the working condition 4 is 0.21 and 0.19, and the two-position damage working condition is met. In summary, the method provided by the invention can effectively identify damage of the three-pipe tower, and particularly to the area range, and the identification result is still correct under the influence of environmental noise, so that the method is still applicable to the condition of changing wind speed and direction.
For the three-pipe tower structure, except for the 4 working conditions, two situations of single damage and multiple damage are considered, multiple damage combination working condition analysis is selected according to the principle of a uniform design method, and the change amount of the D value measuring point after the damage of the rod piece is found to be larger than 0.15. In order to meet the reliability requirement in actual engineering, a 95% confidence interval is taken to refer to a variable load component coefficient of 1.4, a D value is divided by the variable load component coefficient, and the damage preliminary judgment limit value of the D value of the three-pipe tower is conservatively taken to be 0.11.
2.3 Method comparative analysis
As shown in fig. 9, taking the three-tube tower a-plane and the three-tube tower B-plane as an example, the strain fourth-order statistical moment change rate damage identification method provided herein is compared with the modal curvature difference method which also requires initial measurement data. Based on the numerical model, the strain sensor is arranged on the A face, simulation is conducted on the damage working conditions of different areas under 40dB noise, and the damage cases of the 8 th section and the 16 th section structures are selected for specific analysis. The wind speed and the wind direction are kept unchanged, the first-order vibration mode and the strain value before and after the structural damage are respectively extracted, and the results are calculated by using the mode curvature difference and the method disclosed herein, and are shown in figure 10.
The height of the 8 th section corresponding to the structure is near 14m, when the A-plane structure is damaged, the mode curvature difference curve is larger in the 14m abrupt change, and the structure damage area can be identified; however, when the B-plane structure is damaged, misjudgment occurs at a plurality of positions by the mode Qu Lvcha method, and effective recognition cannot be achieved. When the A-plane structure is damaged, the maximum D value at the 16m measuring point is 0.38, and the damage can be identified in the area range of 16m measuring point 3; when the damaged part is far away from the B surface of the measuring point, the D value at the 16m position is changed to 0.22, and the range of the damaged area can still be clearly judged through the D value graph. The 16 th segment has a corresponding structure with a height near 26m, and when different surfaces of the structure are damaged, the mode Qu Lvcha method has mutation around 26m, but other parts have mutation, so that erroneous judgment is caused. When the A-plane structure is damaged, the D value at the 28m measuring point is 0.48, and the D value is the largest in all measuring points; when the surface B is far away from the measuring point, the maximum value of D at the position of 28m is 0.27, and the damage can be effectively judged to be within the range of 28m, namely the measuring point 5. The mode curvature difference method is obtained based on 18 measuring point data analysis of 18 segments in the vertical direction, and the damage identification can be carried out only by 5 measuring points in the vertical direction. Taken together, it is shown that the method herein provides better recognition of tower structure, more noise immunity, and fewer sensors than the modal curve difference method.
3. Verification of field test
And selecting actual measurement data of a certain three-tube communication tower structure in Chongqing Yubei area to verify the engineering applicability of the method. The total of 6 sections (distributed and distinguished according to the main cross rod) of the tower are respectively provided with strain gauges and signal acquisition instruments at 5m, 10m, 16m, 22m and 28m to obtain strain response, the strain sensors are arranged on the main cross rod and on the same plane, and the strain response data of the measuring point 1 is shown in figure 11. And an acceleration sensor and a signal acquisition instrument are arranged at the position 22m to acquire acceleration response in the horizontal direction to identify the frequency of the three-tube tower, and a wind speed and direction sensor and a signal acquisition instrument are arranged at the top of the three-tube tower to record the real-time change of wind speed and wind direction.
And acquiring first-order frequency of the three-tube tower through data of the acceleration sensor, and analyzing by adopting strain response data of the first-order frequency. Referring to the damage identification method principle, a strain fourth-order statistical moment value measured at a certain moment just after installation is taken as an initial value, the current wind speed and wind direction are recorded, the strain fourth-order statistical moment value of the same wind speed and wind direction is calculated after one month, a D value when the wind speed and the wind direction are unchanged is obtained, and a D value bar graph with the wind speed and the wind direction unchanged is drawn. Strain data of the change of the wind speed and the wind direction after a period of time is selected to obtain a strain fourth-order statistical moment value, a reference value is calculated with an initial value, strain data under the same working condition after one month is analyzed to obtain a D value of the change of the wind speed and the wind direction, a D value change amount bar graph after the change of the wind speed and the wind direction is drawn, and a final recognition result is shown in fig. 12.
As can be seen from fig. 12 (a), under the condition that the wind speed and the wind direction are unchanged, the change of the D value of each measuring point is small, the maximum change value is 0.0933, which is smaller than the D value change threshold value of the three-pipe tower by 0.11, and the influence of environmental noise on the D value is considered, so that the three-pipe tower is considered to have no damage during the monitoring period; as can be seen from the result of the condition recognition of the change in the wind speed and the wind direction in fig. 12 (b), when the wind speed and the wind direction are changed, the maximum change of the D value is 0.1065, and is also smaller than the D value change threshold value of 0.11, and it can be still considered that the three-pipe tower is not damaged during the monitoring.
To verify the applicability of the method herein in a three-tube tower injury, the 1 st section bolt and the 3 rd section bolt, which are not in the same plane as the sensor, were unscrewed, respectively. The analysis is carried out by adopting the method proposed by the article, and meanwhile, the comparison analysis is carried out by adopting the method of mode curvature difference, and the identification result is shown in figures 13-14.
As can be seen from fig. 13, the D value change amount at the 5m measurement point is the largest, which indicates that the three-tube tower structure has damage in the 5m measurement point, namely, the area of the measuring point 1. And the D value change amount of the measuring point 1 is 0.2085 when the 1 st section is damaged, the D value change amount of the measuring point 1 is 0.2657 when the 3 rd section is damaged, the D value change amount is larger than the threshold value, the theory is met, the 1 st section is far away from the measuring point 1 than the 3 rd section, the strain energy density change at the position of the measuring point 1 after the damage is smaller than the 3 rd section value, namely the change amount of the strain fourth-order statistical moment change rate caused by the 1 st section damage is smaller than the 3 rd section. As can be seen from fig. 14, the 5 sensors obtain the modal curvature differences corresponding to the 3 measuring points, and the set damage condition cannot be identified. The identification result shows that the damage identification index provided by the method can be considered to be applied to the damage identification of the three-pipe tower actual structure, the number of the sensors to be installed is reduced, and the economic benefit is improved.
4. Conclusion(s)
The article proposes a damage identification method of a communication three-pipe tower structure and carries out related theoretical deduction. Based on analysis of a three-pipe tower numerical model, actual measured response data of an actual communication tower structure are combined for comparison, and the following conclusion is summarized:
1) The strain fourth-order statistical moment change rate damage index is provided, the damage of the local area of the three-pipe tower structure can be identified, the manual investigation workload is reduced, and the method is suitable for quick primary screening of the damage of the three-pipe tower structure.
2) The relation between the fourth-order strain statistical moment and the strain energy density is deduced based on the strain energy density theory, so that the layout of the three-tube tower sensor is optimized, the labor cost is reduced, and the economic benefit is improved.
3) The invention has good noise immunity, has small influence on the change of wind speed and wind direction, and verifies engineering applicability through field test.
In summary, the strain fourth-order statistical moment change rate damage index is provided, the damage of the local area of the three-pipe tower structure can be identified, the manual investigation workload is reduced, the strain energy density sensor is suitable for the rapid initial screening of the damage of the three-pipe tower structure, meanwhile, the relation between the fourth-order strain statistical moment and the strain energy density is deduced based on the strain energy density theory, the layout of the three-pipe tower sensor is optimized, the labor cost is reduced, the economic benefit is improved, in addition, the strain resistance is good, the influence on the change of the wind speed and the wind direction is small, the engineering applicability is verified through the field test, and therefore, the technical problems that the existing damage identification method based on the modal index is insensitive to the local damage and very sensitive to the measurement noise are solved.
The above disclosure is only a preferred embodiment of the present invention, and it should be understood that the scope of the invention is not limited thereto, and those skilled in the art will appreciate that all or part of the procedures described above can be performed according to the equivalent changes of the claims, and still fall within the scope of the present invention.
Claims (7)
1. The novel three-pipe tower damage identification method based on the strain statistical moment is characterized by comprising the following steps of:
step one: a plurality of sensors are uniformly distributed on a three-pipe tower to serve as measuring points, and the sensors are used for collecting strain fourth-order statistical moment values of the measuring points under wind speed and wind direction at a certain moment;
Step two: calculating the strain fourth-order statistical moment value of each measuring point under the wind speed and the wind direction at a certain moment, and setting the moment as an initial value;
step three: under the condition that the wind speed and the wind direction are unchanged, acquiring the strain fourth-order statistical moment value again, and calculating with an initial value to obtain a strain fourth-order statistical moment change rate D as a reference value;
Step four: and calculating the strain fourth-order statistical moment change rate D of the three-tube tower structure under the damage working condition, drawing a D value bar chart, and judging the damage area range of the three-tube tower through the maximum measuring point of the D value.
2. The novel three-pipe tower damage identification method based on the strain statistical moment according to claim 1, wherein,
The measuring points in the step one are arranged on beam units with complex stress combinations, namely the positions of the cross bars on the three-tube tower.
3. The novel three-pipe tower damage identification method based on the strain statistical moment according to claim 2, wherein,
The measuring points in the step one are arranged at all the cross bar positions on the same plane of the three-pipe tower.
4. The novel three-pipe tower damage identification method based on the strain statistical moment according to claim 1, wherein,
And in the first step, the strain fourth-order statistical moment value is extracted depending on a first-order modal parameter which is easier to obtain by the structure of the three-tube tower, and the D value is calculated and analyzed based on a signal after the structure first-order frequency filtering.
5. The novel three-pipe tower damage identification method based on the strain statistical moment according to claim 1, wherein,
The calculation formula of the strain fourth-order statistical moment change rate D in the third step is as follows:
Wherein: Is the strain fourth-order statistical moment value when i measuring points are lossless,/> Is the strain fourth-order statistical moment value when the i measuring point is damaged.
6. The novel three-pipe tower damage identification method based on the strain statistical moment according to claim 1, wherein,
The judging method of the damage area range of the three-pipe tower comprises the following steps: when the wind speed and the wind direction are unchanged, namely external excitation is unchanged, judging damage of the three-pipe tower according to the D value; and when the wind speed and the wind direction change, judging the damage of the three-pipe tower by the change amount of the D value before and after the damage.
7. The novel three-pipe tower damage identification method based on the strain statistical moment according to claim 6,
When the wind speed and the wind direction of the three-pipe tower change, in order to eliminate the global influence of the wind speed and the wind direction on the change of the D value of each measuring point, the D value reference value caused by the change of the wind speed and the wind direction when the structure of the three-pipe tower is not damaged needs to be compared, and the damage identification of the three-pipe tower is further carried out through the change of the D value.
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